The fabrication of semiconductor-based circuitry comprises formation of highly integrated electrical components (with example electrical components being transistors, resistors and capacitors), and thus comprises forming electrical components in close proximity to each other. Insulative materials may be used to electrically isolate various electrical components from one another.
One method of electrically isolating adjacent electrical components from one another is to use trench isolation. Trench isolation may be formed by creating trenches in a semiconductor material, and then filling the trenches with insulative material.
One type of insulative material that may be used to fill the trenches is silicon oxide formed from spin-on dielectric (SOD). Example SODs are polysilazanes. When polysilazanes are utilized as SODs, the formation of silicon oxide may comprise multiple steps. Initially, spin-on methodology may be used to fill trenches with polysilazane. Subsequently, the polysilazane within the trenches may be converted to silicon oxide by exposing the polysilazane to oxidant and appropriate thermal conditions.
A common method for converting a polysilazane to silicon oxide is to use steam densification. Specifically, the polysilazane is exposed to steam while being maintained at a temperature of at least 585° C.
A problem with such steam densification is that oxidant can penetrate through the polysilazane and into semiconductor material adjacent the polysilazane. Thus, it is common to provide a silicon nitride liner within the trenches prior to filling the trenches with polysilazane. The silicon nitride liner can function as a barrier during steam densification of the polysilazane, with such barrier protecting underlying semiconductor material from oxidation during the steam densification.
In some applications it would be desirable to utilize SODs, but to omit the silicon nitride barriers. Accordingly, it would be desirable to develop new methods for utilizing SODs during fabrication of isolation structures.